Charging materials by friction
3 marks · NormalExplain, in terms of electrons, how a polythene rod becomes negatively charged when rubbed with a woolen cloth.
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Electrons transfer from the woolen cloth to the polythene rod, so the rod gains electrons and becomes negatively charged.
Also accept: Electrons move from the cloth onto the rod, giving it extra electrons.
Common mistakes: Saying protons move between objects.
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Marking points
M1 · 1 mark · Mentions electrons move (from one object to the other).
M1 · 1 mark · Points out electrons move from cloth to rod.
A1 · 1 mark · Relates gain of electrons to negative charging of rod.
Worked solution
When the polythene rod is rubbed with wool, electrons move from the woolen cloth to the polythene rod. As a result, the polythene gains electrons and becomes negatively charged.